A third of all board appointments over the next four years would have to be
women to meet Lord Davies' target to have females make up a quarter of UK
FTSE 100 boards.

The former trade minister said that one-in-three of all UK board appointments must be female to achieve the voluntary target set for 2015. That equates to 135 females being hired.

The proposal came amid a raft of recommendations to the Government to increase the number of females on boards – women hold just 12.5pc of positions currently.

Lord Davies stopped short of calling for mandatory quotas but gave warning that they remained a threat if voluntary measures failed.

Among the proposals, the review called for listed companies to draw up a boardroom diversity policy and publicly report the number of women at board level, in senior roles and in the wider company.

The recruitment process for senior appointments should be more transparent – with non-executive board posts "periodically" advertised – and headhunters should sign up to a new code to address gender balance, Lord Davies said.

Executive search firms have been urged to cast the net far wider than they currently do to identify talented females, drawing up shortlists including women entrepreneurs, academics and civil servants. Headhunters tended to focus on women with financial backgrounds or who had served on executive committees, Lord Davies said.

Investors should also play a greater role in holding companies to account when considering company reporting and board appointments, according to the review.

Business groups broadly welcomed the decision not to introduce quotas. However, the CBI said companies should report against internal targets that reflected different starting points and sectors. Helen Alexander, CBI president, said: "It should be for companies, not the Government, to set an appropriate target."

However, some employment experts warned the review did not go far enough to address inequality. Dawn Nicholson, HR consulting partner at PricewaterhouseCoopers, said: "The risk is that these targets, which are highly aspirational, will simply encourage employers to hire in senior women without dealing with the far more complex issue of why women are failing to progress within their organisations in the first place. This is like painting over a damp wall."

Senior FTSE female executives said the review should have focused more on how to nurture women early on for board roles.

Laura Whyte, personnel director at John Lewis, said: "If you have talent succession and development programmes in place throughout the organisation then the most talented people emerge and that will be a mixture of men and women."